When a cigarette is smoked, visible smoke is produced, by mainstream smoke spillage, exhale smoke and as well sidestream smoke which is generated by the burning cigarette between puffs. This smoke is considered objectionable by some persons and this has led to no-smoking laws of varying degrees of strictness in certain jurisdictions and environments.
A number of prior proposals have been made with respect to structures which are designed to minimize or eliminate the formation of visible cigarette smoke. Such prior proposals have tackled the major source of cigarette smoke; namely that derived from sidestream smoke and exhale smoke. It is appreciated that the mainstream smoke spillage is a very minor portion of visible smoke. However, no device disclosed in the prior art known to the applicants provides for the elimination of substantially all the visible sidestream and exhale smoke and also provides the same smoking taste and quality to the smoker as if smoked in the normal way.
One prior structure is disclosed in U.S. Pat. No. 4,790,332. This patent describes a hand-held enclosure in which is positioned the lighted cigarette. Smoking is effected through a holder formed in one end wall of the device and in which the filter-end of the cigarette is mounted. Exhalation of smoke is effected through a one-way valved passageway formed in the same end wall of the device as the holder, permitting exhale smoke to pass into the enclosure. The opposite end wall as well as the side walls of the enclosure have a tobacco smoke filter provided therein, to filter the particulate and odoriferous elements from the smoke leaving the enclosure. This arrangement, while substantially eliminating visible smoke and the characteristic smell of tobacco smoke, suffers from the drawback that the smoke present in the enclosure, as a result of static burning or exhale, causes an off-flavour to be introduced to the tobacco smoke drawn by the smoker through the cigarette into his mouth.
U.S. Pat. No. 4,198,992 describes a device in which the cigarette again is enclosed for smoking. No provision is made in this instance for the disposal of exhale smoke. The device employs air pressure in the enclosure to force sidestream smoke through the cigarette.
U.S. Pat. No. 4,200,114 describes a device in which the cigarette again is enclosed for smoking. The device provides for disposal of both sidestream smoke and exhale smoke. The device in use is permanently mounted to the face of a smoker, with a mask enveloping the smoker's mouth and nose. A complicated series of check valves permits air to be drawn for breathing and to be exhaled into a combustion chamber in which the lit cigarette is positioned, and from which air and smoke passes through a filter to atmosphere, and permits cigarette smoke to be drawn from the cigarette.
U.S. Pat. No. 4,899,766 describes a device for disposal of sidestream smoke and exhale smoke. A fan is used in conjunction with filters to draw sidestream smoke and, while exhaled through a hand activated valve, exhale smoke, into a pipe for further passage through the filters.
U.S. Pat. No. 5,048,545 describes a system in which sidestream smoke and exhale smoke are collected in a container which only later is vented. There is no treatment of the smoke contemplated only the collection thereof.
U.S. Pat. No. 4,637,407 describes an enclosure for a burning cigarette intended to protect against fires started by the burning tip of the cigarette. A forced flow of air, by way of a small fan, is provided to maintain the cigarette lit and sidestream smoke removal is effected by a filter downstream of the fan. No provision is made in this structure for the disposal of exhale smoke.
U.S. Pat. 4,993,435 discloses a smoker's accessory which captures sidestream smoke for inhalation by the user and is provided with an exhale filter arrangement. Several serially arranged filter discs are provided.
U.S. Pat. No. 5,160,518 discloses a smoker's accessory which comprises a U-shaped tube. The lit cigarette is placed in one leg of the U-shaped tube and the exhale filter is placed in the other leg of the U-shaped tube. A fan is mounted in front of the lit cigarette to direct fresh air at the end of the cigarette and through the exhale filter. Several one-way valves are employed to direct either sidestream smoke or exhale smoke through the single filter before release to the surroundings. The filter is made of activated carbon, which although useful in removing gaseous components in cigarette smoke is not that effective for removing particles from the cigarette smoke. As a result the filtered smoke when released to the surroundings is still detectable and hence not acceptable. Furthermore, the cigarette is encased in a small diameter metal tube which carries with it the problems identified with respect to the other devices where the cigarette is not burned in a normal manner so that the taste and flavour of the inhaled smoke is greatly affected.
Another form of hand-held cigarette smoke filter is disclosed in Japanese published patent application HEI3-177280 published Apr. 27, 1993. The application discloses a device in which a cigarette is placed. A mouth piece is provided to permit inhalation of the cigarette smoke. Any sidestream smoke is filtered by surrounding filters. However, when the cigarette is inhaled the stale sidestream smoke is also inhaled thereby greatly affecting flavour and taste. A one-way valve is employed to ensure that smoke exhaled into the unit is directed through a filter before release to the surroundings. A small metal tube surrounds the lit cigarette which greatly affects the flavour and taste of the inhaled smoke.
Considerable efforts have been made in the area of filters as provided on cigarettes to effect a partial filtration to reduce the amount of tar and nicotine inhaled by the user. It is appreciated that cigarette filters however are not designed to remove substantially all of the cigarette smoke so that the smoker continues to experience the usual sensations. There have been however cigarette filters which are tubular in nature and designed to filter some of the smoke particles from the smoke stream. U.S. Pat. No. 3,685,523 discloses a tubular cigarette tip filter which partially filters the cigarette smoke as it passes from the interior of the tubular filter to the exterior thereof for inhale by the smoker. A similar type of filter is described in U.S. Pat. No. 3,854,384 involving a tubular filter only offset with respect to the central axis of the cigarette. Both filters are however of marginal performance so as to not remove the various components of cigarette smoke which give the user the desired taste and flavour.
Canadian Patent 1,057,924 as issued to the applicant describes a method of producing polymeric fibres of micron size which can be used in cigarette filters. Such micro-fibre has been used in cigarette filters of the type described in applicant's U.S. Pat. No. 3,882,877 and International patent application WO90/09741. The micro-fibres produced by the method of Canadian Patent 1,057,924 have increased filtration efficiency compared to cigarette filters of the standard cellulose acetate, charcoal and the like. In order to take advantage of the efficiency of those filters a thin cylindrical filter is provided in the filter tip of a cigarette as described in WO90/09741 which provides for uniform tar delivery while smoking the cigarette.